Chapter 6: mesoscale gravity waves

This ppt summarizes the slides in the textbook. The theory is covered in class.

Note: this ppt does not include section 6.6 Bores.

Iowa gravity wave time lapse movie mpeg

You Tube

UK

Ireland

cold front

5/24/2002, 21:07 UTC – IHOP

Aral Sea

Australia

Australia

Fig. 6.1: isochrones of a mesoscale gravity wave crest during a major East Coast snowstorm. The wave was detected in the pressure trace. The wind barbs indicate the vector surface wind shift upon wave passage.

x Greensboro (GSO)

dry adiabat (q=46°C)

moist adiabat (qw=16°C)

qw values (°C) Fig. 6.9: the mesoscale gravity wave event may have been triggered by elevated convection, or gravity wave adjustment.

The stable low-level layer may have allowed wave ducting towards the NE.

Fig. 6.11: synoptic setting of gravity wave activity (p’~ a few mb)

Fig. 6.2: SLP analysis in a Midwest snowstorm. dotted lines: wave crests, dashed lines: troughs

Fig. 6.10: schematic of a linear plane mesoscale gravity wave propagating to the right (Uo=0)

see youtube video

Fig. 6.6: polarization relations between q’, p’, u’, and w’ in a westward tilting internal gravity wave

blue = cold, red = warm

Critical level: level where wave energy is absorbed

cg

c

Fig. 6.7Fig. 6.8

geostrophic adjustment: principle

Rossby radius of deformation:

see COMET module “the balancing act of geostrophic adjustment”

see YouTube video:geostrophic adjustment: inertio-gravity waves and the Coriolis force

𝐿𝑅=𝑐𝑔𝑟𝑎𝑣𝑖𝑡𝑦 𝑤𝑎𝑣𝑒

𝑓 ≅ 𝑁𝐻𝜋√ 𝑓 𝜁

Will a feature last or dissipate? Estimate its LR

6.6 undular bores and solitary waves:separate slide show